The present invention relates to irrigation systems and pertains particularly to an improved pilot valve assembly for solenoid actuated irrigation control valves.
The use of valve controlled pressurized irrigation systems for supplying water for the irrigation of plants is extensive throughout the world today. One of the most prevalent systems, particularly for lawn areas and playing or athletic fields, is the sprinkler system wherein a plurality of sprinkler units are positioned about a land area for distributing water over the surface of the land area. One or more control valves connect and disconnect water from a pressurized main supply line to one or more branch lines having sprinkler units.
Commercial, industrial, municipal and golf course irrigation systems increasingly rely on alternative water sources including reclaimed water as an irrigation water source. This trend has been prompted by an often critical need to conserve water in most regions of the country. Other alternative water sources include lakes, reservoirs, wells, and the like. However, since water from these sources often contains dirt, sand and other particles and debris, its use has brought with it an increase in the incidence of clogging of various components of irrigation systems. While the obvious solution is simply to filter the water entering the irrigation system, the cost of such filters, and their maintenance, limits the degree of filtering that is economically feasible.
The problem of clogging in irrigation systems is most acute in areas in the system where water must pass into and around small spaces and through small openings. Such systems having small openings occur, for example, in irrigation systems having pilot operated and pressure responsive control valves, pressure regulating valves, in drip systems, and in other low flow irrigation configurations. Another area where dirt and debris cause problems is where the water comes into contact with moving parts. One example where such problems occur is in small solenoid operated plunger valves which have a small valve seal on the end of a plunger which extends into a water passage and acts as a pilot valve.
Pressure responsive and pressure regulating valves used in irrigation systems typically have a main diaphragm valve that is normally pilot operated. Upstream or inlet water pressure passes via a small passage to the back of the main diaphragm valve to apply valve closing pressure. The water is vented from the back of the diaphragm valve via a small passage controlled by a solenoid operated pilot valve to the down stream side of the valve.
The pilot valve is normally operated by a plunger of a solenoid that moves back and forth in a bore in a housing surrounded by a coil with the valve seal being an elastomeric disc on the end of the plunger which selectively engages a valve seat. The water controlled by the pilot valve typically flows around and frequently along between the pilot valve plunger and its housing either during pressurization or venting of the control valve. Dirt and debris in the water frequently jam between the plunger and its housing preventing its normal operation. Sealing around or between the plunger and its housing is difficult because the plunger must be free to move and air or other fluids must be free to move in and out of the bore along the plunger.
Accordingly, there is a need for an irrigation control valve with a solenoid that is protected from contamination.